"We're in a really good place," Cox revealed on "Good Morning America." We're "probably the best we've ever been because we're being really honest with each other. We have such huge amounts of affection for each other."
Cox, 46, said it's all about their six-year-old daughter Coco.
"We have 15 years of memories. There's no point in spoiling that," she said. "I don't know what's going to happen, but I think this is an important time and he will always be my guy."
Cox and Arquette met each other on the set of the first "Scream" movie. For "Scream 4," Cox reprised her role as tabloid reporter Gale Weathers, who's married to Arquette's David Dewey, but by the time filming rolled around, their on-screen characters were having problems and their 11-year marriage was falling apart.
We "fell in love on the first, hated each other on the second, got married right before the third and...what are you talking about, what's wrong? Is there some news about us?" she joked with Robin Roberts on "GMA."
Cox and Arquette separated in October 2010. Arquette, 39, is celebrating 90 days of sobriety after a tumultuous 2011. The actor was in a head-on car collision in Los Angeles in March, entered a rehab program for alcohol abuse and depression in January. That came after weeks of public confessions, including his admitting on Howard Stern's radio show that "I am definitely having a nervous breakdown."
Arquette has also been loose-lipped on "The Howard Stern Show" about his relationship with Cox, spilling intimate details about their sex life or lack thereof. Cox said on "GMA" she's not angry with Arquette for oversharing.
"David's so funny. He's a showman. He knows what he's doing and he's having fun. He loves doing the show and I'm a big Howard fan," Cox said. "David's got such a big heart so even if he says things like, 'Wow, really?' I don't know why, I just don't really have any problem with it."
Both Cox and Arquette hit the red carpet of "Scream 4's" premiere Monday night. While Cox arrived hand-in-hand with co-star Neve Campbell, Arquette arrived solo.
Cox said "Scream 4," coming out Friday, gives the first film a run for its money.
"I really do believe it's as good as the first," Cox said. "It's really funny, the cast is amazing … The acting is good…obviously [director Wes Craven] knows how to scare you like nobody else."
Cox started watching horror films at a young age.
"I think I was 13 when I snuck in to see 'The Exorcist.' I went with a girlfriend and she left…and I stayed. And I think I've been tormented forever," she said.